Known level measuring instruments have a parabolic antenna, which emits or receives radar or microwaves for determining the filling level of a medium in a filling material container. In this case, the parabolic antenna of such a level measuring instrument is arranged e.g. inside a container.
The quality of the measuring signals received at level measuring with a level radar having a parabolic antenna largely depends on the quality of the transmitting-receiving unit. In particular, contamination of the antenna feed or the exciter, which may be caused e.g. by filling material dust or liquid, may significantly deteriorate the quality of measuring results. In the extreme case, serious contamination of the exciter (which by the way may also be used as a radiation receiver) may even lead to no signals being transmitted at all.